[s-cars] safe boost limits - Wastegate 101

[Paul Krasusky]

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<<<I will try to live up to the quality commentary so widely given here
:-)>>>

For better or for worse...  we all know which is the case with mine in
particular...

-Paul


-----Original Message-----
From: Mark Strangways [mailto:strangconst at rogers.com]
Sent: Thursday, September 19, 2002 10:28 AM
To: QSHIPQ at aol.com; S4audinut at aol.com; KrasuskyP at FirstInterBank.com;
s-car-list at audifans.com
Subject: Re: [s-cars] safe boost limits - Wastegate 101


While this is all great read,

    I would like it to be known that
        a) I have not removed the WGFV, I was just trying to clarify what I
thought was accurate against the varied response presented.
        b) I don't intend to every remove the WGFV now or in the future.
        c) I don't intend to use a manual boost controller, although I was
considering trying that manual idea with the regulator etc. But not anymore.
        d) I intend on a bigger turbo, and a RPFR as I think it might help
richen up the fuel fixture at max boost. (waiting on the responses on that
one ... :-) ).
        e) Will be installing a 3" trubo back Stromung when I get it (
thanks Jeff !).
        f) Or Audi Gods willing, I don't intend on rebuilding  the AAN motor
in my car .
            ( Well, if that lottery ticket wins.... )
        g) I have not taken anything the wrong way ( Just in case someone
reads it the wrong way).

I want to say what a great list this is, and wish I had been participating
in it years ago when I first heard about it.
I will try to live up to the quality commentary so widely given here :-)

best regards to all.
keep up the good work

Mark Strangways.

93' S4 with to much boost
----- Original Message -----
From: <QSHIPQ at aol.com>
To: <S4audinut at aol.com>; <strangconst at rogers.com>;
<KrasuskyP at FirstInterBank.com>; <s-car-list at audifans.com>
Sent: Thursday, September 19, 2002 10:10 AM
Subject: Re: [s-cars] safe boost limits - Wastegate 101


> No Rod.  Large WG springs (or adding preload to the stock) add low end
> torque, because you are changing the ramping of the WGFV circuit (please
> continue reading, I don't consider this a *good* thing).  If you put in a
> 1.5bar spring for instance, when the WGFV wants to trim boost, it can only
> trim it to 1.5bar.  A 1.5 bar spring however will only allow 1.5 bar boost
> without WGFV assist.  The only time I've seen boost "added" to the high
end,
> was putting on a 2.2bar spring on a 2.1bar car.
>
> So the assessment is correct as stated, Adjusting WGFV preload does
little,
> and the baseline spring pressure (WGFV fully open) is 1.3-1.4bar (5-6psi).
> You may or may not see that depending on the mods you have in your car.
For
> instance, a huge turbo with WGFV bypassed will pop the WG WFO (a
combination
> of turbo map and wastegate cracking).  By definition, if there is a spring
in
> a wastegate, with *no* electronic control, you must have some boost.
>
> I recommend *against* messing with WG springs.  They are there to protect
> your engine investment.  A better way to address the crappy WGFV is to
adapt
> a stepper motor into the software. Stepper motors are much more accurate
than
> the FV approach audi chose.  The problem with them is that the software
has
> to be changed to accomodate them.
>
> Also note:  Bypassing the WGFV isn't a good idea either.  Remember,
without a
> software change or a input fault, the computer will be looking for that
> 16/22/26psi, and will ramp your turbo up to overcome the WG blowoff.  If
all
> goes well in this scenario, your MAF will code you out before you blow the
> turbo.  That is not always the case, btst.
>
> HTH
>
> Scott Justusson
> QSHIPQ Performance Tuning
>
>
>
>
> In a message dated 9/18/02 2:09:25 PM Central Daylight Time,
> S4audinut at aol.com writes:
>
>
> > From what I have read on the list the wastegate spring limits max boost
to
> > only 1.3 bar Abs, and the WGFV is what is allowing the overboost to get
> > where it is.
> > Is this a correct assumption, if so... winding down the wastegate would
do
> > little, would it not.
> >
> >
>
> No, The WG spring has more to do with getting these unacceptably high
levels
> (unless engine totally built) than any SW. I have some VERY aggressive SW
and
> it doesnt run this high when not in overboost.
> Rod
>